Contaminated earth at Canadian Forces Station Alert is piled up in preparation for cleaning by bacteria found in the soil. Photo credit: National Research Council
Mopping up a diesel fuel spill is never easy, especially at the world’s most northerly habitation on Ellesmere Island, where spring, summer and fall are over in about eight weeks and the ground remains frozen the rest of the year. Nevertheless, members of the Department of National Defence (DND) and the National Research Council of Canada (NRC) successfully tackled this challenge by recruiting bacteria found in that same soil.
The problem started in 2006 when damage to a new fuel pipeline near the airfield at Canadian Forces Station Alert (CFS Alert) spilled some 22,000 litres of DF-8. Fast work with heavy equipment built trenches to contain the liquid and kept it from running into the nearby ocean, creating a pile of about 3,700 cubic metres of contaminated soil.
Dealing with that pile — and others like it — fell to Drew Craig, the 8 Wing Environmental Management Officer at CFB Trenton. Craig and his small team are responsible for five DNC sites across the country, including CFS Alert, where they had already been struggling with how to remediate soils in this extreme setting.
In warmer, more fertile locations, a healthy dose of fertilizer can prompt bacteria in soil to slowly and steadily consume diesel fuel. However, earlier attempts to stimulate such activity at Alert had failed to do so. Craig’s group had already been working on remediation strategies with researchers at the NRC’s Energy, Mining and Environment program in Montreal, so they began to collaborate on a different approach for this latest spill. “Given the fact that soil in the far North is very poor in terms of its nutrient content, it made sense to the NRC to experiment with lower concentrations of monoammonium phosphate fertilizer as a starting point,” says Craig. “As it turned out, the optimal concentration of fertilizer to soil is about a tenth of that which would be used to treat soil in southern Canada.”
According to NRC research officer David Juck, this finding illustrates how dramatically the parameters for bacterial remediation can vary from one type of soil to the next. In each case, the key is identifying the balance of parameters, such as nutrient load, oxygen concentrations and pH that will be necessary for those bacteria to thrive. “When we’re going into these sites we’re really trying to re-establish the balance that was there prior to the contamination event,” he says. “In most systems it’s a nice balance between the ratio of carbon to nitrogen to phosphorus. Once you have a diesel gas spill, you skew that ratio to significantly more carbon. The nitrogen and phosphorus are consumed very quickly and bacteria wind up with a nutrient deficit.”
Although the calculations to correct that deficit were a complicated affair, the final steps were as simple as flying bags of store-bought fertilizer into Alert and spreading it along windrows of contaminated soil. That process began in 2007 and eight years later — which amounts to about a year of non-frozen biological activity — the job is finally done.
Results from August 2015 indicated that F-2 hydrocarbon concentrations in the biopile soil were below Canadian Council of Minister of the Environment criteria. The clean soil will be returned to the site of origin, Craig says.
This accomplishment introduces a new way of dealing with contamination in the Arctic, where treatment options have been fairly limited. Juck also points out that this work serves as an important reminder that environmental matters can often be best handled with the biological resources that are available close by. “Who better to address these issues than the bacteria that are naturally present on this site?”